Means for oscillating one of a pair of relatively rotatable members

ABSTRACT

One of the members has a track raised thereon which is equipped with arcuate surfaces on opposite sides thereof, that are concentric with the rotational axis of the members, and joined to one another at the corresponding ends thereof. The other member extends transversely of the track between the aforesaid opposite sides thereof, and has a wheel rotatably carried threreon, the rotational axis of which is parallel to the axis of the members but transversely shiftable in relation thereto. The wheel is yieldably biased into engagement with the surface of the track, on each side thereof, and the members are rotated in relation to one another by driving the wheel in one rotational direction thereof, so as to cause either the wheel or the track to undergo rotation about the axis of the members, there being yieldable biasing means for retaining the wheel in engagement with the track as it crosses the junctures between the surfaces at their ends.

United States Patent 1 Rothenbuhler et a1.

[ MEANS FOR OSCILLATING ONE OF A PAIR OF RELATIVELY ROTATABLE MEMBERS[75] Inventors: Howard E. Rothenbuhler, Acme;

Primary ExaminerManuel A. Antonakas Assistant Examiner-Wesley S.Ratliff, Jr.

A ttor ney Christensen," '"o*r:banor, Garrsion Havelka Robert C. Melder,Sedro Woolley;

John Lawrence Cotter, Mt. Vemqn,

all of Wash.

[73] Assignee: Rothenhuhler Engineering ABSTRACT Company, Sedro Woolley,Wash.

Apr. 3, 1972 One of the mei'nbers has a track raised thereon which isequipped with arcuate surfaces on opposite sides there [22] Filed:

of, that are concentric with the rotational axis of the members, andjoined to one another at the corre- [21] Appl. No.: 240,647

sponding ends thereof. The other member extends transversely of thetrack" between the aforesaid opposite sides thereof, and has a wheelrotatably carried threreon, the rotational axis of which is parallel tothe axis of the members but transversely shiftable in relation thereto.The wheel is yieldably biased into en gagement with the surface of thetrack, on each side there of, and the members are rotated in relation toMm u-l u C mi- N u m m m Q m n m mW b mT o mw RSCSMS .M 25482 mooibw 00999 NHHHHH U16398 83492 97398 nws u 3 3 3 one another by driving thewheel in one rotational directionthereof, so as to cause either thewheel or the track to undergo rotation about the axis of the members,there being yieldable biasing means for retaining the wheel inengagement with the track as it crosses the junctures between thesurfaces at their ends.

24 Claims, 14 Drawing Figures 2,433,274 12/1947 Hapman............'.....

PAIENTEDUEB 4% 3776047 SHEET 10F 3 PATENTEDBEB Mws- 3776047 SHEET 2 BF 3MEANS FOR OSCILLATING ONE A PAIR OF RELATIVELY ROTATABLE MEMBERS OBJECTSOF THE, INVENTION One object of the present invention is to provide ameans and technique for converting the motor-driven unidirectionalangular motion of a rotatable input member, into reciprocable angularmotion on the part of one or the other of a pair of relatively rotatableoutput members. Another object is to provide a means and technique ofthis nature wherein the relative angular displacement of the outputmembers can be varied between an arc of little more than zero degrees,and an are approaching 360 degrees. Still another object is to provide ameans and technique of this nature wherein the relative reciprocablemotion of the output members can be reversed, almost instantly, byreversing the angular direction of the input member, as for example, byreversing the direction of the motor which operates to drive the same. Afurther object is to provide a means and technique of this naturewhereby the relatively rotatable output members can be spaced narrowlyapart from one another, and the input member can be accommodated in thespace therebetween to produce a highly compact oscillatory arrangement.A still further object is to provide a means and technique of thisnature whereby the arrangement is assembled and constructed fromrelatively few components other than the input and output membersthemselves. Other objects include the provision of a means and techniqueof this nature whereby the few additional components are commonlyrelatively inexpensive components such as springs and/or simplelever-mounted roller assemblies; and all of the components in thearrangement are capable of extended lives, even under conditions ofcontinuous operation, because of the small number of wear surfaces, andthe low operating speeds which may be employed. Still further objectswill become apparent from the description of the invention which followshereafter.

SUMMARY OF THE INVENTION These objects and advantages are realized by ameans and technique of our invention wherein one of the relativelyrotatable output members has a track raised thereon which is equippedwith arcuate surfaces on opposite sides thereof, that are concentricwith the rotational axis of the members and joined to one another at thecorresponding ends thereof. The other member extends transversely of thetrack between the aforesaid sides thereof, and has a wheel rotatablycarried thereon, the rotational axis of which is parallel to the axis ofthe members but transversely shiftable in relation thereto. The wheel isyieldably biased into engagement with the surface of the track, on eachside thereof, and the members are rotated in relation to one another bydriving the wheel in one rotational direction thereof, so as to causeeither the wheel or the track to undergo rotation about the axis of themembers, there being yieldable biasing means for retaining the wheel inengagement with the track as it crosses the junctures between thesurfaces at their ends.

The wheel retainer means is displaceable against the bias thereof, indirections crosswise the axis of the members, and may be disposed on therelatively stationary member and engageable with the relativelyrotatable member to load the wheel against the junctures between thesurfaces; or it may be disposed on the relatively rotatable member andengageable with the relatively stationary member for this purpose. Forexample, in certain of the presently preferred embodiments of theinvention, the wheel retainer means is mounted on the track bearingmember and engageable with either the wheel or the wheel bearing member,to load the wheel against the junctures between the surfaces. In othersuch embodiments, it is mounted on the wheel bearing member andengageable with the track for this purpose. In these latter embodiments,moreover, the retainer means is also operable to yieldably bias thewheel into engagement with the surfaces of the track.

The wheel may be shiftable along a radial line through the axis of themembers, or it may be shiftable crosswise of such a line. For example,the wheel may be outriggered on a carriage which is shiftable along theline; or it may be outriggered on a leaf spring which is disposedcrosswise of the line, and has the wheel adjacent the outlying endthereof. Preferably, the spring is cantilevered from the other member ata point on the side of the track opposite from the rotational axis ofthe members, and extends to a point between the axis and the track, thewheel being carried on the spring adjacent the latter point.

Also, it is preferred that the other member take the form of an arm,acting either as a gantry rail for the carriage, or as an outrigger boomfor the leaf spring. In certain embodiments, moreover, the boom and thespring may be combinedas a V-shaped leaf spring, cantilevered by one endfrom a shaft, with the bight thereof disposed at a point on the side ofthe rail opposite from the shaft.

The track is preferably defined by a rail which is upstanding on the onemember. The rail may have a single-walled cross section, the oppositesides of which form the surfaces of the track; or it may have a spaced,

double-walled cross section, the relatively remote sides of which formthe surfaces of the track.

In the single-walled construction, the wheel retainer means may includea yieldably biased bumper element adjacent each juncture of the rail.The bumper element may take the form of a leaf spring which is anchoredto the one member at one end, and disposed adjacent the juncture of therail to engage the other member when the wheel approaches the juncture;or the bumper element may take the form of a roller which is rotatablymounted on a spring-loaded lever that is pivotally mounted on the onemember to yieldably engage the roller with the juncture of the rail.

In the double-walled construction, the wheel retainer means may includea yieldably biased clamping wheel interposed between the walls of therail.

BRIEF DESCRIPTION OF THE DRAWINGS These features will be betterunderstood by reference to the accompanying drawings which illustratethree of the presently preferred embodiments.

In the drawings, Y

FIG. 1 is a perspective view of the mechanism em ployed in oneembodiment; I

FIG. 2 is a plan view of this mechanism in one operational conditionthereof;

FIG. 3 is a side elevational view of the mechanism in this condition;

FIG. 4 is a part cross-sectional view of the mechanism in this samecondition;

FIG. 5 is another plan view of the mechanism illustrating both the otheroperating condition and the changeover of the mechanism from onecondition to the other;

FIG. 6 is a perspective view of the mechanism employed in a secondembodiment;

FIG. 7 is a schematic illustration of the means by which the mechanismundergoes a changeover of operating condition;

FIG. 8 is a similar illustration of a means by which the mechanism issafeguarded against slippage;

FIG. 9 is an elevational illustration of the latter means;

FIG. 10 is a perspective view of the mechanism employed in the thirdembodiment;

FIG. 11 is a part cross-sectional view of the mechanism;

FIG. 12 is a similar view of the mechanism at a different stage in itsoperation;

FIG. 13 is a part elevational view of the mechanism along the line 1313of FIG. 11; and

FIG. 14 is a part plan view of the mechanism along the line 14-14 ofFIG. 11.

DESCRIPTION OF TI-IEPREFERRED EMBODIMENTS Referring to FIGS. 1-5 of thedrawings, it will be seen that the mechanism in the first embodimentcomprises a square-shaped plate 2 having an eccentrically locatedaperture 4 therein, and an arcuate rail 6 upstanding thereon about thecenter of the aperture. The rail 6 is spotwelded to the near edge of theplate 2 in FIG. 1, and in addition, is secured to the far corners of theplate by right angular brackets 8 which are attached to the railslightly inboard from the bladed ends 10 thereof. The rail serves as atracking surface for a wheeled, motor-driven crank device 12 which iserected upright in the aperture 4 and supportably journaled within aroller bearing 14 that is bolt-clamped to the rim of the aperture 4between the plate 2 and a colla: 16 superposed thereon. The crank device12 comprises a flat, horizontally disposed crank arm 18, the inner end18' of which is bifurcated and pinch-screwclamped onto a pintle-likearbor 20 for the same, constructed from a threaded pipe section having apair of nuts 22 thereon which serve to locate the arbor in the bearing14. The arm 18 extends to a point outside the rail 6, where there is anelongated leaf spring 24 secured to a right angular bracket 26 on theupper side of the outlying end thereof. The spring 24 is acutelyreentrantly angled to the arm in a vertical plane, so as to extendtransversely of the rail to a point inside thereof. At this point, thespring has an apertured right angular bracket 30 attached to one sidethereof, which in turn has a cylindrically apertured collar 28 seated onthe horizontal leg thereof, to provide a saddle for an electric motor 32which is mounted upright in the collar, with the shaft 34 thereofdepending vertically through the aperture in the bracket, and carrying avertically oriented, cylindrical wheel 36 thereon.

The crosswise disposition of the spring 24 with respect to the rail 6,is such that the wheel 36 is yieldably biased into engagement with therail, whether the wheel is disposed inside or outside of the same. Thus,when the motor 32 is energized, the wheel 36 bears against the adjacentconvex or concave surface 6' or 6", respectively, of the rail, andtracks along the surface from one end 10 thereof to the other. Thetracking of the wheel causes the crank device 12 to rotate in turn aboutthe axis of the arbor 20, there being, however, a pair of upright leafsprings 38 and 40 bracketed to the base plate 2, adjacent the ends 10 ofthe rail, which intercept the arm 18 as the wheel 36 approaches eitherend 10 of the rail When the arm is so engaged, the wheel leaves thesurface and, reacting to the bias of the spring 38 or 40, tracks ontoand about the blade at that end, until it eventually reverses itsdirection along the opposite surface of the rail. See FIG. 5 where thearm has abutted the spring 38 as the wheel approached the left-hand endof the rail after travelling along the concave surface 6" thereof; orconversely, abuts the spring 40 so as to reverse the course of thedevice in the opposite direction about the right-hand end of the rail,after the wheel has travelled along the convex surface 6' of the same.

The second embodiment also comprises an apertured squareshaped baseplate 42 having an arcuate rail 44 upstanding thereon which is fixed tothe plate about the center of the aperture 46 therein. In this instance,however, the plate and rail are rotatably joumaled about a fixed shaft48 which is equipped with a pair of spaced collars 50 and 52 forlocating the plate 42 thereon. The shaft 48 has a round-bighted V-shapedleaf spring 54 cantilevered by one end therefrom, which crisscrossesabove the rail 44 in such a fashion as to place the bight 54 of the sameoutside the rail, and the free-end 54" of the same inside of the rail.This latter end 54" is equipped with a laterally projecting flange orbracket 56 thereon, and a motor-driven wheel 58 is outriggered on theflange so as to remain engaged with the rail under the bias of thespring. When the wheel is rotated, the tracking action of the wheelcauses the rail and plate to rotate about the shaft; and when thecontinued rotation of the same brings the approaching end of the rail toa point of coincidence with the wheel, the wheel engages one of a pairof rollers 60 which are rotatably mounted on the free-ends of a pair ofspring-loaded levers 62 that are pivotally mounted in turn on the plate42 to yieldably engage the rollers with the ends of the rail as in FIG.6. The respective roller 60 engages the wheel and acts to maintain it onthe rail, as the wheel crosses the juncture between the concave andconvex surfaces thereof, the illustration of FIG. 7 illustrating themode of this action, although in schematic tenns only, since asindicated, the rail in fact travels in relation to the wheel, contraryto the illustration.

A pin 64 on the wheel assures that the wheel continuously tracks aroundthe end of the rail, in that the pin will engage an upstanding pin 66 onthe end of the rail as soon as slippage starts to occur.

In the third embodiment of FIGS. 10-14, the square shaped base plate 68has an arcuate, double-walled ribbon rail 70 upstanding thereon, theinside and outside walls of which, 72 and 74, respectively, are spacedapart from one another but joined to one another at the correspondingends thereof by rounded bight sections 76. Superimposed about the centerof the plate is a bearing 78 which has an upright shaft 80 rotatablyjournaled therein. Cantilevered from the top of the shaft is acrank-device 81 comprising a horizontally extending crank arm 82 whichis flat and oriented in a vertical plane to form a gantry rail for amotor-driven tracking device 84 at the outlying end thereof. Thetracking device 84 comprises a bracket-like carriage 86 which is movablyengaged on the arm 82 by means of three peripherally-grooved rollers 88journaled to the back of the L-shaped bracket 90 thereof. The bracketforms a saddle for an electric motor 92 which is mounted uprightthereon, with the shaft 94 thereof depending vertically through anaperture in the bracket 90, and carrying a vertically orientedcylindrical drive wheel 96 thereon. The wheel 96 is yieldably biasedinto engagement with the walls 72 and 74 of the ribbon rail 70, andretained on the rail at the bights 76 thereof, by means of aspring-loaded clamping wheel 98 which is disposed on the inside of therail, between the walls thereof. The clamping wheel 98 is carried in aU-shaped, yoke-like bracket 100 which is joumaled about the shaft 94 ofthe drive wheel 96, on a bearing 102, and comprised of a slottedL-shaped base portion 104, and a pair of spaced parallel arms 106extending reentrantly therefrom. The spindle 108 of the clamping wheel98 is trunnioned between the arms 106, and depends within the slot 110of the base portion, to suspend the wheel 98 therebelow. To load thewheel 98 against the rail 70, a coiled spring 112 is caged between theupright wall 104 of the base portion 104 and a shoe 114 on the spindle108. The spring 112 operates to bias the wheels 96 and 98 relativelytoward one another, the carriage 86 meanwhile shifting lengthwise of thearm 82 to accommodate for the distance between the walls 72 and 74 ofthe rail, and the bracket 100 likewise swivelling about the shaft 94 ofthe wheel 96 to follow the travel of the wheels 96 and 98 from one wallto the other.

In lieu of an electric motor, other drive means may be employed, such asa pneumatic, hydraulic, or springdriven motor. Likewise, othermodifications and additions can be made in and to the invention withoutdeparting from the scope of the same as defined in the claims following.

What is claimed is:

1. In combination, a pair of relatively rotatable members, one of whichmembers has an arcuate track raised thereon, the ends of which arespaced apart from one another and the relatively convex and concavesurfaces of which are concentric with the rotational axis of the membersand joined to one another at the ends of the track, and the other ofwhich members extends transversely of the track between the surfacesthereof, and

has a wheel rotatably carried thereon, the rotational axis of whichwheel is parallel to the axis of the members but transversely shiftablein relation thereto, the wheel being yieldably biased into engagementwith the track, and there being means for rotating the wheel about theaxis thereof, to cause the wheel and the track to reciprocate inrelation to one another, relatively about the axis of the members, andyieldable biasing means operative to retain the wheel in engagement withthe track when the wheel reaches the respective ends of the track,whereby the wheel relatively traverses alternate surfaces of the track,and traverses from surface to surface across alternate juncturestherebetween.

2. The combination according to claim 1 wherein the wheel retainer meansis displaceable against the bias thereof, in directions crosswise theaxis of the members, and is disposed on the relatively stationarymember, and engageable with the relatively rotatable member to load thewheel against the junctures between the surfaces.

3.v The combination according to claim 1 wherein the wheel retainermeans is displaceable against the bias thereof, in directions crosswisethe axis of the members, and is disposed on the relatively rotatablemember, and engageable with the relatively stationary member to load thewheel against the junctures between the surfaces.

4. The combination according to claim 1 wherein the wheel retainer meansis mounted on the track-bearing member, and engageable with either thewheel or the wheel bearing member to load the wheel against thejunctures between the surfaces.

5. The combination according to claim 1 wherein the wheel retainer meansis mounted on the wheel bearing member, and engageable with the track toload the wheel against the junctures between the surfaces.

6. The combination according to claim 5 wherein the wheel retainer meansis also operable to yieldably bias the wheel into engagement with thesurfaces of the track.

7. The combination according to claim 1 wherein the wheel is shiftablealong a radial line through the axis of the members.

8. The combination according to claim 1 wherein the wheel is shiftablecrosswise of a radial line through the axis of the members.

9. The combination according to claim 7 wherein the wheel is outriggeredon a carriage which is shiftable along the line.

10. The combination according to claim 8 wherein the wheel isoutriggered on a leaf spring which is disposed crosswise of the line andhas the wheel adjacent the outlying end thereof.

11. The combination according to claim 10 wherein the spring iscantilevered from the other member at a point on the side of the trackopposite from the rotational axis of the members, and extends to a pointbetween the axis and the track, the wheel being carried on the springadjacent the latter point.

12. The combination according to claim 9 wherein the other member takesthe form of an arm, acting as a gantry rail for the carriage.

13. The combination according to claim 10 wherein the other member takesthe form of an arm, acting as an outrigger boom for the leaf spring.

14. The combination according to claim 13 wherein the boom and thespring are combined as a V-shaped leaf spring, cantilevered by one endfrom a shaft, with the bight thereof disposed at a point on the side ofthe rail opposite from the shaft.

15. The combination according to claim 1 wherein the track is defined bya rail which is upstanding to the one member.

16. The combination according to claim 15 wherein the rail has asingle-walled cross section, the opposite sides of which form thesurfaces of the track.

17. The combination according to claim 15 wherein the rail has a spaced,double-walled cross section, the relatively remote sides of which formthe surfaces of the track.

18. The combination according to claim 16 wherein the wheel retainermeans includes a yieldably biased bumper element adjacent each junctureof the rail.

19. The combination according to claim 18 wherein the bumper elementtakes the form of a leaf spring which is anchored to the one member atone end, and

disposed adjacent the juncture of the rail to engage the I other memberwhen the wheel approaches the juncture.

20. The combination according to claim 18 wherein the bumper elementtakes the form of a roller which is rotatably mounted on a spring-loadedlever that is pivotally mounted on the one member to yieldably engagethe roller with the juncture of the rail.

21. The combination according to claim 17 wherein the wheel retainermeans includes a yieldably biased clamping wheel interposed between thewalls of the rail.

22. In combination, a pair of relatively rotatable members, one of whichmembers has a track raised thereon which is equipped with arcuatesurfaces on opposite sides thereof, that are concentric with therotational axis of the members, and joined to one another at thecorresponding ends thereof, and the other of which members extendstransversely of the track between the aforesaid opposite sides thereof,and has a wheel rotatably carried thereon, the rotational axis of whichwheel is parallel to the axis of the members but transversely shiftablein relation thereto, the wheel being yieldably biased into engagementwith the surface of the track on each side thereof, there being meansfor driving the wheel in one rotational direction thereof, to causeeither the wheel or the track to undergo rotation about the axis of themembers, and yieldable biasing means for retaining the wheel inengagement with the track as the wheel crosses the junctures between thesurfaces at their ends, the wheel being outriggered on a leaf springwhich is disposed crosswise of a radial line through the axis of themembers, and which is cantilevered from the other member at a point onthe side of the track opposite from the rotational axis of the members,and extends to a point between the axis and the track, the wheel beingcarried on the spring adjacent the latter point.

23. In combination, a pair of relatively rotatable members, one of whichmembers has a track raised thereon which is equipped with arcuatesurfaces on opposite sides thereof, that are concentric with therotational axis of the members, and joined to one another at thecorresponding ends thereof, and the other of which members extendstransversely of the track between the aforesaid opposite sides thereof,and has a wheel rotatably carried thereon, the rotational axis of whichwheel is parallel to the axis of the members but transversely shiftablein relation thereto, the wheel being yieldably biased into engagementwith the surface of the track of each side thereof, there being meansfor driving the wheel in one rotational direction thereof, to causeeither the wheel or the track to undergo rotation about the axis of themembers, and yieldable biasing means for retaining the wheel inengagement with the track as the wheel crosses the junctures between thesurfaces at their ends, the wheel being outriggered on a V-shaped leafspring which is cantilevered by one end from a shaft, with the bightthereof disposed at a point on the side of the track opposite from theshaft, and with the wheel carried adjacent the outlying end thereof. 7

24. The combination according to claim 1 wherein the wheel isfrictionally engaged with the track.

PO-1050 UNITED S'lATES PATENT OFFICE @ERTEHCATE UP QQRREC'E Patent No.3Q'Z76JQAE'Y Dated D Inventor(s) Howard E(, Rothenbuhler et a];

It is certified that error appears in the above-identified patent andthat said Letters Patent are hereby corrected as shown below:

Claim 1;, line 8; delete "between the surfaces thereoff'u Claim 15, line2, change "to" to -on-.

Signed and sealed this 9th day of A ril 19m,

(SEAL) Attest Z EDWARD M GFLETCHEIR,JRO C. MARSHALL DANN Attest'ingOfficer Commissioner of Patents

1. In combination, a pair of relatively rotatable members, one of whichmembers has an arcuate track raised thereon, the ends of which arespaced apart from one another and the relatively convex and concavesurfaces of which are concentric with the rotational axis of the membersand joined to one another at the ends of the track, and the other ofwhich members extends transversely of the track between the surfacesthereof, and has a wheel rotatably carried thereon, the rotational axisof which wheel is parallel to the axis of the members but transverselyshiftable in relation thereto, the wheel being yieldably biased intoengagement with the track, and there being means for rotating the wheelabout the axis thereof, to cause the wheel and the track to reciprocatein relation to one another, relatively about the axis of the members,and yieldable biasing means operative to retain the wheel in engagementwith the track when the wheel reaches the respective ends of the track,whereby the wheel relatively traverses alternate surfaces of the track,and traverses from surface to surface across alternate juncturestherebetween.
 2. The combination according to claim 1 wherein the wheelretainer means is displaceable against the bias thereof, in directionscrosswise the axis of the members, and is disposed on the relativelystationary member, and engageable with the relatively rotatable memberto load the wheel against the junctures between the surfaces.
 3. Thecombination according to claim 1 wherein the wheel retainer means isdisplaceable against the bias thereof, in directions crosswise the axisof the members, and is disposed on the relatively rotatable member, andengageable with the relatively stationary member to load the wheelagainst the junctures between the surfaces.
 4. The combination accordingto claim 1 wherein the wheel retainer means is mounted on thetrack-bearing member, and engageable with either the wheel or the wheelbearing member to load the wheel against the junctures between thesurfaces.
 5. The combination according to claim 1 wherein the wheelretainer means is mounted on the wheel bearing member, and engageablewith the track to load the wheel against the junctures between thesurfaces.
 6. The combination according to claim 5 wherein the wheelretainer means is also operable to yieldably bias the wheel intoengagement with the surfaces of the track.
 7. The combination accordingto claim 1 wherein the wheel is shiftable along a radial line throughthe axis of the members.
 8. The combination according to claim 1 whereinthe wheel is shiftable crosswise of a radial line through the axis ofthe members.
 9. The combination according to claim 7 wherein the wheelis outriggered on a carriage which is shiftable along the line.
 10. Thecombination accOrding to claim 8 wherein the wheel is outriggered on aleaf spring which is disposed crosswise of the line and has the wheeladjacent the outlying end thereof.
 11. The combination according toclaim 10 wherein the spring is cantilevered from the other member at apoint on the side of the track opposite from the rotational axis of themembers, and extends to a point between the axis and the track, thewheel being carried on the spring adjacent the latter point.
 12. Thecombination according to claim 9 wherein the other member takes the formof an arm, acting as a gantry rail for the carriage.
 13. The combinationaccording to claim 10 wherein the other member takes the form of an arm,acting as an outrigger boom for the leaf spring.
 14. The combinationaccording to claim 13 wherein the boom and the spring are combined as aV-shaped leaf spring, cantilevered by one end from a shaft, with thebight thereof disposed at a point on the side of the rail opposite fromthe shaft.
 15. The combination according to claim 1 wherein the track isdefined by a rail which is upstanding to the one member.
 16. Thecombination according to claim 15 wherein the rail has a single-walledcross section, the opposite sides of which form the surfaces of thetrack.
 17. The combination according to claim 15 wherein the rail has aspaced, double-walled cross section, the relatively remote sides ofwhich form the surfaces of the track.
 18. The combination according toclaim 16 wherein the wheel retainer means includes a yieldably biasedbumper element adjacent each juncture of the rail.
 19. The combinationaccording to claim 18 wherein the bumper element takes the form of aleaf spring which is anchored to the one member at one end, and disposedadjacent the juncture of the rail to engage the other member when thewheel approaches the juncture.
 20. The combination according to claim 18wherein the bumper element takes the form of a roller which is rotatablymounted on a spring-loaded lever that is pivotally mounted on the onemember to yieldably engage the roller with the juncture of the rail. 21.The combination according to claim 17 wherein the wheel retainer meansincludes a yieldably biased clamping wheel interposed between the wallsof the rail.
 22. In combination, a pair of relatively rotatable members,one of which members has a track raised thereon which is equipped witharcuate surfaces on opposite sides thereof, that are concentric with therotational axis of the members, and joined to one another at thecorresponding ends thereof, and the other of which members extendstransversely of the track between the aforesaid opposite sides thereof,and has a wheel rotatably carried thereon, the rotational axis of whichwheel is parallel to the axis of the members but transversely shiftablein relation thereto, the wheel being yieldably biased into engagementwith the surface of the track on each side thereof, there being meansfor driving the wheel in one rotational direction thereof, to causeeither the wheel or the track to undergo rotation about the axis of themembers, and yieldable biasing means for retaining the wheel inengagement with the track as the wheel crosses the junctures between thesurfaces at their ends, the wheel being outriggered on a leaf springwhich is disposed crosswise of a radial line through the axis of themembers, and which is cantilevered from the other member at a point onthe side of the track opposite from the rotational axis of the members,and extends to a point between the axis and the track, the wheel beingcarried on the spring adjacent the latter point.
 23. In combination, apair of relatively rotatable members, one of which members has a trackraised thereon which is equipped with arcuate surfaces on opposite sidesthereof, that are concentric with the rotational axis of the members,and joined to one another at the corresponding ends thereof, and theother of which members extends transversely of the track between theaforesaid Opposite sides thereof, and has a wheel rotatably carriedthereon, the rotational axis of which wheel is parallel to the axis ofthe members but transversely shiftable in relation thereto, the wheelbeing yieldably biased into engagement with the surface of the track ofeach side thereof, there being means for driving the wheel in onerotational direction thereof, to cause either the wheel or the track toundergo rotation about the axis of the members, and yieldable biasingmeans for retaining the wheel in engagement with the track as the wheelcrosses the junctures between the surfaces at their ends, the wheelbeing outriggered on a V-shaped leaf spring which is cantilevered by oneend from a shaft, with the bight thereof disposed at a point on the sideof the track opposite from the shaft, and with the wheel carriedadjacent the outlying end thereof.
 24. The combination according toclaim 1 wherein the wheel is frictionally engaged with the track.